Objective To search for the cause for the high-temperature color change of cyanide-free silver coating, in order to enhance the discoloration resistance of the cyanide-free silver coating at high temperature. Methods Thiosulfate system was used to plate silver on the copper sheet, followed by baking at 300 ℃ (without inert gas protection) for 1 h. Scanning electron microscopy (SEM) was used to observe the microstructure of the coating after high-temperature baking, and energy spectrometer (EDS) was used to detect the content and distribution of elements in the coating. The effects of silver layer thickness, power supply mode, and the post-processing technology on the discoloration resistance of the coating at high temperature were discussed. Results When the thickness of direct current (dc) plating layer was 9 μm and the thickness of pulse electroplating layer was 6 μm, the coating did not change color after high-temperature baking. But the coatings (with a thickness of 6 μm) after treatment with water soluble silver protectant, potassium dichromate, and PMTA all changed color after high-temperature baking. Scanning electron microscopy showed convex-shape cracks on the surface of the high-temperature discolored coating, and spectrometer detected copper atoms leakage phenomenon. Conclusion Leakage of copper atoms at high temperature led to discoloration of the coating. Pulse plating could decrease the porosity of the coating. Increasing the silver coating thickness and using the pulse plating could improve the high-temperature discoloration resistance of silver coating.